import random
lst=[]
for i in range(10,101):
    lst.append(i)
while True:
    x=random.choice(lst)
    y=random.choice(lst)
    print(x, end='-')
    print(y, end='')
    m = eval(input('='))
    if m==x-y:
        print('答对了')
    else:
        while True:
            print('答错了，再试一遍')
            print(x, end='-')
            print(y, end='')
            m = eval(input('='))
            if m == x - y:
                print('答对了')
                break
            else:
                continue
    print('-' * 20)



